“Super-slugs” are invading British gardens – and we don’t know how to stop them

Mmmmmm, slimy. Image: Xauxa Håkan Svensson.

The Daily Mail calls it a “slime wave”. The Sun calls them “an army”. Either way, both papers have reported 500bn slugs are set to invade British gardens, after a mild winter created perfect breeding conditions. The Conversation

So is the UK really about to be overwhelmed by slimy slugs? The simple answer is no, but there could be something far worse in store.

Headline numbers alone aren’t necessarily something to get in a lather over. A typical garden can contain several thousand slugs, and the “500bn” figure is derived from estimates of maximum numbers per area. In any case, slug numbers can rise and fall a great deal across time and space, in natural cycles, and even astonishingly dramatic increases are not always cause for concern. Like waves crashing against a beach, the rise is often transient and local – usually slug numbers will drop back to normal, with the disturbance hardly noticed beyond a few local gardeners.

What is more problematic is the progressive, sustained and perhaps less spectacular rise in numbers which, tsunami-like, is maintained for far longer, and spreads widely throughout the countryside. This is Britain’s real slug invasion. So what can we do about it?

The trigger seems innocuous enough in isolation: a few non-native slugs from continental Europe have accidentally been introduced. Several of these species have close relatives in the UK, so similar in fact that only specialists can tell them apart, and they can interbreed freely. Of course, many animals can create hybrids without presenting a threat, but what makes slugs different – and these hybrids so worrying – is their interesting and deviant sex lives.

This is a hybrid between a ‘Spanish stealth slug’ and the UK’s common black slug. Image: Les Noble/author provided.

Slugs are hermaphrodites, which means the same individual exists as both sexes; they first develop as males, before experiencing a true hermaphrodite phase to become female. This means they can dispense with normal mating requirements, and this is where the consequences of the difference between British and continental species becomes significant.

Why British slugs are different

When slugs colonised the UK after the last ice age, they found an island recently covered with ice sheets, where the biological diversity remained poorer than continental Europe. In these circumstances, the ability to self-fertilise was a good evolutionary strategy, one which ensured reproduction even when slug populations were devasated by harsh weather.

A downside of such continued close inbreeding (and mating with oneself is as inbred as it gets) is a rapid loss of genetic variability, and some British slug species eventually came to consist of almost genetically identical individuals. This meant they were more vulnerable to parasites and pathogens that could rapidly evolve to overcome their defences.

Meanwhile, in continental Europe, slugs were becoming more diverse, as balmier weather meant parasites and pathogens were a bigger issue than finding a mate. These slugs tended not to self-fertilise, and were genetically highly variable. This made at least some of them more resilient to attacks from parasites – a possibility not afforded to the inbred British slugs.

Echoes of these different past environments resonate in contemporary species. British slugs, adapted to a variable climate and dearth of mates, have fallen into the clichéd “No sex please, we’re British” mould, producing fewer, bigger eggs later in life by self-fertilisation. Continental slugs, meanwhile, adapted to resist rapidly evolving enemies. Their strategy is therefore to produce many smaller eggs earlier in life, which maximises genetic diversity and compensates for losing many individuals to infection.

The ‘Spanish slug’, one of Britain’s key invaders. Image: tviolet/creative commons.

These different adaptations weren’t an issue until humans disturbed the natural order by moving slugs back and forth as stowaways in commercial produce. As a result of this, we’ve seen widespread breeding between British and continental species. These new hybrid “super-slugs” are highly fertile, and their genetically diverse offspring are adapted to cope with both the British climate and parasites and pathogens, most of which remain in continental Europe anyway.


Fighting the slug invasion?

Legislation aimed at environmental protection has led to the EU banning commercial use of molluscicides (pelleted chemicals which poison slugs but cause collateral damage to other wildlife). Instead, the emphasis is on using natural enemies like nematode worms, though these are generally ineffective against the larger invasive hybrids.

Nonetheless, the increased slug biomass could still host important veterinary or agricultural parasites and pathogens, spreading more plant and animal diseases. Remarkably, despite their obvious presence in our gardens, we remain startlingly ignorant of the fundamental biology of slugs; evidenced by recent work which increased the number of identified British species by more than a fifth.

So where are we going with this phenomenon? Studies have already found invasive slugs and snails can destabilise ecosystems and reduce biodiversity in the US and Scandinavia. Something similar is happening here in the UK.

The good news is that our research suggests population sizes do eventually begin to decline, after 30 to 40 years. The ecosystem may eventually rebound from this slug invasion, but it remains to be seen how long it will take and what the lasting effects will be for the spread of diseases, ecosystem services, or British biodiversity.

Leslie Noble is a reader in zoology at the University of Aberdeen.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Owning public space is expensive. So why do developers want to do it?

Granary Yard, London. Image: Getty.

A great deal has been written about privately owned public space, or POPS. A Guardian investigation earlier this year revealed the proliferation of “pseudo-public spaces”. Tales of people being watched, removed from or told off in POPS have spread online. Activists have taken to monitoring POPS, and politicians on both sides of the pond are calling for reforms in how they are run.

Local authorities’ motives for selling off public spaces are normally simple: getting companies to buy and maintain public space saves precious public pounds. Less straightforward and often overlooked in this debate is why – given the maintenance costs, public safety concerns and increasingly unflattering media attention – developers would actually want to own public space in the first place.

To answer that question it’s important to note that POPS can’t be viewed as isolated places, like parks or other public spaces might be. For the companies that own them, public spaces are bound up in the business that takes place inside their private buildings; POPS are tools that allow them, in one way or another, to boost profits.

Trade-offs

In some cities, such as Hong Kong and New York, ownership of public space is a trade-off for the right to bend the rules in planning and zoning. In 1961 New York introduced a policy that came to be known as ‘incentive zoning’. Developers who took on the provision of some public space could build wider, taller buildings, ignoring restrictions that had previously required staggered vertical growth to let sunlight and air into streets.

Since then, the city has allowed developers to build 20m square feet of private space in exchange for 80 acres of POPS, or 525 individual spaces, according to watchdog Advocates for Privately Owned Public Space (APOPS).

Several of those spaces lie in Trump Tower. Before the King of the Deal began construction on his new headquarters in 1979, he secured a pretty good deal with the city: Trump Tower would provide two atriums, two gardens, some restrooms and some benches for public use; in exchange 20 floors could be added to the top of the skyscraper. That’s quite a lot of condos.

Shockingly, the current president has not always kept up his end of the bargain and has been fined multiple times for dissuading members of the public from using POPS by doing things like placing flower pots on top of benches – violating a 1975 rule which said that companies had to provide amenities that actually make public spaces useable. The incident might suggest the failure of the ‘honour system’ under which POPS operate day-to-day. Once developers have secured their extra square footage, they might be tempted to undermine, subtly, the ‘public’ nature of their public spaces.

But what about where there aren’t necessarily planning benefits to providing public space? Why would companies go to the trouble of managing spaces that the council would otherwise take care of?


Attracting the ‘right sort’

Granary Square, part of the £5bn redevelopment of London’s Kings Cross, has been open since 2012. It is one of Europe’s largest privately-owned public spaces and has become a focal point for concerns over corporate control of public space. Yet developers of the neighbouring Coal Drop Yards site, due to open in October 2018, are also making their “dynamic new public space” a key point in marketing.

Cushman Wakefield, the real estate company in charge of Coal Drops Yard, says that the vision of the developers, Argent, has been to “retain the historical architecture to create a dramatic environment that will attract visitors to the 100,000 square feet of boutiques”. The key word here is “attract”. By designing and managing POPS, developers can attract the consumers who are essential to the success of their sites and who might be put off by a grubby council-managed square – or by a sterile shopping mall door.

A 2011 London Assembly Report found that the expansion of Canary Wharf in the 1990s was a turning point for developers who now “assume that they themselves will take ownership of an open space, with absolute control, in order to protect the value of the development as a whole”. In many ways this is a win-win situation; who doesn’t appreciate a nice water feature or shrub or whatever else big developer money can buy?

The caveat is, as academic Tridib Banerjee pointed out back in 2001: “The public is welcome as long as they are patrons of shops and restaurants, office workers, or clients of businesses located on the premises. But access to and use of the space is only a privilege and not a right” – hence the stories of security guards removing protesters or homeless people who threaten the aspirational appeal of places like Granary Square.

In the US, developers have taken this kind of space-curation even further, using public spaces as part of their formula for attracting the right kind of worker, as well as consumer, for nearby businesses. In Cincinnati, developer 3CDC transformed the notoriously crime-ridden Over-The-Rhine (OTR) neighbourhood into a young professional paradise. Pouring $47m into an initial make-over in 2010, 3CDC beautified parks and public space as well as private buildings.

To do so, the firm received $50 million  in funding from corporations like Procter and Gamble, whose Cincinnati headquarters sits to the South-West of OTR. This kind of hyper-gentrification has profoundly change the demographics of the neighbourhood – to the anger of many long-term residents – attracting, essentially, the kind of people who work at Procter and Gamble.

Elsewhere, in cities like Alpharetta, Georgia, 3CDC have taken their public space management even further, running events and entertainment designed to attract productive young people to otherwise dull neighbourhoods.

Data pools

The proposed partnership between the city of Toronto and Sidewalk Labs (owned by Google’s parent company Alphabet) has highlighted another motive for companies to own public space: the most modern of all resources, data.

Data collection is at the heart of the ‘smart city’ utopia: the idea that by turning public spaces and the people into them into a vast data pool, tech companies can find ways to improve transport, the environment and urban quality of life. If approved next year, Sidewalk would take over the mostly derelict east waterfront area, developing public and private space filled with sensors.

 Of course, this isn’t altruism. The Globe and Mail describe Sidewalk’s desired role as “the private garbage collectors of data”. It’s an apt phrase that reflects the merging of public service and private opportunity in Toronto’s future public space.

The data that Sidewalk could collect in Toronto would be used by Google in its commercial projects. Indeed, they’ve already done so in New York’s LinkNYC and London’s LinkUK. Kiosks installed around the cities provide the public with wifi and charging points, whilst monitoring traffic and pedestrians and generating data to feed into Google Maps.

The subway station at Hudson Yards, New York City. Image: Getty.

This is all pretty anodyne stuff. Data on how we move around public spaces is probably a small price to pay for more efficient transport information, and of course Sidewalk don’t own the areas around their Link Kiosks. But elsewhere companies’ plans to collect data in their POPS have sparked controversy. In New York’s Hudson Yards development – which Sidewalk also has a stake in – ambiguity over how visitors and residents can opt out of sharing their data when in its public square, have raised concerns over privacy.

In Toronto, Sidewalk have already offered to share their data with the city. However, Martin Kenney, researcher at the University of California at Davis and co-author of 2016’s ‘The Rise of the Platform Economy’, has warned that the potential value of a tech company collecting a community’s data should not be underestimated. “What’s really important is the deals Toronto cuts with Sidewalk may set terms and conditions for the rest of the world," he said after the announcement in October.

The project could crystallise all three motives behind the ownership of POPS. Alongside data collection, Sidewalk will likely have some leeway over planning regulations and will certainly tailor its public spaces to its ideal workers and consumers – Google have already announced that it would move its Canadian headquarters, from their current location in Downton Toronto, into the first pilot phase of the development.

Even if the Sidewalks Lab project never happens, the motives behind companies’ ownership of POPS tell us that cities’ public realms are of increasing interest to private hands.

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